Multiple hygienic articles, such as feminine hygiene products (e.g., pantiliners or pads), disposable diapers, pull-ons, training pants, and adult incontinence articles, are often provided in a stack that is maintained within a package, such as a carton or a bag. Consumers expect that the total number of hygienic articles that is printed on the package are actually included in the package. Conventionally, a checkweigher is used to weigh the packages, and based on a floating average target weight, the package is deemed whether or not to have a sufficient count of pads within it. Unfortunately, raw material weight variation is too great for checkweighing to be a reliable count verification method.
An alternative method of verifying the number of hygienic articles within a package is to use a stack counting vision system, which inspects the stack of hygienic articles immediately before it is loaded into the package. Thus, depending on the inspection result, the package will be rejected if the stack has an unexpected count. However, current vision systems utilize edge detection to count the number of objects that are present within an image generated by the vision system. Hygienic articles, such as feminine hygiene products, are inherently pliable such that their edges are difficult to detect by edge detection methodologies. Further, some hygienic articles contain a separate release paper, such as a release paper on pantiliners, for example, that may become slightly separated and erroneously counted as an individual hygienic article within the stack.